kbuild: Fix __start_SECTION, __stop_SECTION

In a discussion with Sam Ravnborg, the following problem became apparent:
Most vmlinux.lds.S (but the ARM ones) used the following construct:
  
       __start___ksymtab = .;                                          
       __ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {         
               *(__ksymtab)                                            
       }                                                               
       __stop___ksymtab = .;                                           
  
However, the link will align the beginning of the section __ksymtab
according to the requirements for the input sections. If '.' (current
location counter) wasn't sufficiently aligned before, it's possible
that __ksymtab actually starts at an address after the one
__start___ksymtab points to, which will confuse the users of
__start___ksymtab badly. The fix is to follow what the ARM Makefiles
did for this case, ie
  
       __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) {                 
               __start___ksymtab = .;                                  
               *(__ksymtab)                                            
               __stop___ksymtab = .;                                   
       }                                                               

include/asm-generic/vmlinux.lds.h

@@ -13,18 +13,18 @@
 	}								\
 									\
 	/* Kernel symbol table: Normal symbols */			\
-	__start___ksymtab = .;						\
 	__ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {		\
+		__start___ksymtab = .;					\
 		*(__ksymtab)						\
+		__stop___ksymtab = .;					\
 	}								\
-	__stop___ksymtab = .;						\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
-	__start___gpl_ksymtab = .;					\
 	__gpl_ksymtab     : AT(ADDR(__gpl_ksymtab) - LOAD_OFFSET) {	\
+		__start___gpl_ksymtab = .;				\
 		*(__gpl_ksymtab)					\
+		__stop___gpl_ksymtab = .;				\
 	}								\
-	__stop___gpl_ksymtab = .;					\
 									\
 	/* Kernel symbol table: strings */				\
         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {	\